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iterating over list and removing items

Posted on 2013-10-30
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Last Modified: 2016-02-17
I'm running into a logic problem and I'm hoping someone can help.  I using the Salesforce apex language, but it is similar to Java and C# so I'm posting in both the c# and java topic areas as the syntax is similar.

I'm using a simple for loop structure:

    		for(Integer i=0; i < contactLinesForPage.size(); i++) {
    			if(contactLinesForPage[i].selected == false) {
    				contactLinesForPage.remove(i);
    			}
    		}

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I have a list of records and I'm checking to see which records have been selected.  If the record has not been selected, I'm removing it from the list.  So, I should end up with a list of only the records that have been selected.  

As the list size goes down and the iterator goes up, it does not end up removing all my items that were not selected from the list.

For example, let's say 6 records are returned and the user selects 1 record.  When I finish iterating over the list, I should just have 1 record, but I end up with 3 records (1 that was selected by the user and 2 records that were not selected).

I know my loop logic is flawed, but can someone help explain what I need to do to correctly iterate over my records and remove the items from the list that were not selected?

Any help is appreciated.
Thanks.
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Question by:-Dman100-
2 Comments
 
LVL 29

Accepted Solution

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Paul Jackson earned 500 total points
ID: 39612915
This is because the value for is changing when you remove items from the list so instead declare a List variable called selectedContactLinesForPage and add items from contactLinesForPage to it when you have detected they are selected.
for(Integer i=0; i < contactLinesForPage.size(); i++) {
    			if(contactLinesForPage[i].selected == true) {
    				SelectedContactLinesForPage.Add(contactLinesForPage[i]);
    			}
    		}

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LVL 35

Expert Comment

by:mccarl
ID: 39613091
Either the above, or you can decrement the loop counter inside the if statement, such as ...
    		for(Integer i=0; i < contactLinesForPage.size(); i++) {
    			if(contactLinesForPage[i].selected == false) {
    				contactLinesForPage.remove(i);
    				i--;
    			}
    		}

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